Method of estimating a distance

Abstract

The invention relates to a method of estimating a distance to a surface, whereby an emitter emits light towards a surface, at least some light being reflected by the surface, the surface comprising a detectable feature, the reflected light being received by a first receptor and by a second receptor, the surface being in movement relative to the receptors, the first and the second receptor receiving the light reflected at a first and at a respectively second angle thereby producing a first and a respectively second dataset, each dataset including data representing said feature, the first and the second angle being different, whereby the distance is estimated using the first and the second dataset.

1. A method of estimating a distance to a surface, comprising: an emitter emitting light towards a surface, at least some light being reflected by the surface, the surface comprising a detectable linear feature, wherein the surface is an upper surface of a printing medium and the feature is an edge of the printing medium; receiving the reflected light by a first receptor and by a second receptor, the surface being in movement relative to the receptors, the first and the second receptor receiving the light reflected at a first and at a respectively second angle; and producing a first and a respectively second dataset, each dataset including data representing said feature, the first and the second angle being different, whereby the distance is estimated using the first and the second dataset. 
     
     
       2. A method according to  claim 1 , whereby the feature is printed on the printing medium. 
     
     
       3. A method according to  claim 1 , whereby the emitter, the first and the second receptors are located on a printhead carriage. 
     
     
       4. A method according to  claim 1 , whereby the method is part of a method of estimating the thickness of a medium. 
     
     
       5. A method according to  claim 4 , whereby the method is optimized to measure a thickness comprised in the range of 0.1 to 2 mm with a resolution of less than 0.2 mm. 
     
     
       6. A method according to  claim 1 , whereby the first receptor is a specular light receptor. 
     
     
       7. A method according to  claim 1 , whereby the second receptor is a diffuse light receptor. 
     
     
       8. A method according to  claim 1 , whereby the emitted light is emitted at an angle substantially equal to the first angle. 
     
     
       9. A calibration method whereby the thickness of a printing medium is linked to a first and to a second output, comprising: outputting the first output from a first optical receptor, and the second output from a second optical receptor; the first optical receptor receiving light at a first angle for estimating the thickness of the printing medium; the second optical receptor receiving light at a second angle for estimating the thickness of the printing medium; wherein the first and the second output are shifted, and evaluating the shift between the first and the second output, whereby a function is built comprising a linear function relating the shift to the thickness; and wherein the first and the second angle are different. 
     
     
       10. A method according to  claim 9 , whereby the link is provided by scanning the surface of a medium having a known thickness, the surface comprising a detectable feature, the feature being scanned and detected by the first and by the second optical receptor. 
     
     
       11. A method according to  claim 9 , whereby the first output and the second output have a similar profile. 
     
     
       12. A method according to  claim 9 , whereby the first and the second output are in the form of a first and respectively second dataset. 
     
     
       13. A method according to  claim 9 , whereby the method is part of a printer calibration procedure. 
     
     
       14. A system for estimating a distance to a surface, comprising: an emitter configured to emit light towards a surface, at least some light being reflected by the surface, the surface comprising a detectable feature, wherein the surface is an upper surface of a printing medium and the detectable feature is an edge of the printing medium; and a first receptor and a second receptor, the first and second receptors configured to receive the reflected light, the surface being in movement relative to the first and second receptors, the first and second receptors receiving the light reflected at a first and at a respectively second angle thereby producing a first and a respectively second dataset, each dataset including data representing the feature, the first and second angles being different, whereby the distance is estimated using the first and second datasets. 
     
     
       15. A system according to  claim 14 , whereby the surface is the upper surface of a printing medium, the feature is an edge of the printing medium, and the feature is printed on the printing medium. 
     
     
       16. A system according to  claim 14 , whereby the emitter and the first and second receptors are located on a printhead carriage. 
     
     
       17. A system according to  claim 14 , whereby the system is configured to estimate the thickness of a medium.